The Reactor (originally called Halberds Reactor) is the core power source of the Halberd. Without it operational, the ship will not be able to power its engines, so it is equipped with its own automatic defenses. It appears as a boss in the Revenge of Meta Knight stage of Kirby Super Star and its remake, Kirby Super Star Ultra, and as a mid-boss at the end of the Battleship Halberd level of Kirby's Epic Yarn. In each iteration, it's a large, stationary machine with one or more cannons attached, holding a gem (which is presumed to be its power source). It's unique in the fact the reactor itself cannot be damaged by Kirby, but only by the lasers it shoots to attack.
Kirby Super Star
|So long as a reflected laser doesn't hit the reactor, it will be invincible.|
— Sailor Waddle Dee, Revenge of Meta Knight - Chapter 6, Kirby Super Star Ultra
|Eeeyah! Don't even say things like that!|
— Captain Vul, Revenge of Meta Knight - Chapter 6, Kirby Super Star Ultra
The reactor is a large, round, brown-ish machine with a shining, color-changing gem as its power source. The machine stretches to the top of the screen and has a large, horizontal hole holding the gem with four spikes jutting upwards from the lower part of the machine and a decently large cannon pointing forwards. In the background, numerous Wheelies can be seen driving back and forth, seemingly used as batteries, with blue wires connecting the compartments together. The reactor is located on a grate-like floor and is positioned on the right side of the screen. It will not move apart from smaller compartments that it uses to attack; a small, nozzle-like compartment it uses to fire lasers, the cannon on the front of the machine and up to three boxes it uses to spout fire through the grate floor. After the boss is defeated, the wheelies escape, and the scene transitions to the stage where Kirby rides one of the Wheelies across the Halberd in order to escape the ensuing explosion. This boss also shows up in The Arena.
- Laser: A small blue turret will appear from the top of the screen and angle itself to aim at Kirby. It shoots of a single laser that must be redirected towards the gem to damage the reactor. The turret can be destroyed, but will reappear.
- Cannon: The cannon at the front is almost always exposed. It attacks by charging up, then shooting two spiraling fireballs horizontally. If Kirby gets hit by these, he will get burned. This cannon can be permanently destroyed, but this is not required to defeat the boss.
- Flame Pillars: The reactor sends forth up to 3 box-like machines underneath the floor. They will pause for a second before blasting pillars of fire upwards through the floor. These can be destroyed, but will reappear.
Kirby Super Star Ultra
Little was changed between the two versions, though this reactor has had a slight redesign. There are now 5 spikes on both the top and bottom compartment of the machine, all of which are adorned with small, blue balls. The gem now radiates in multiple colors as well. The box under the floor are more visible and the background shows more mechanisms between the Wheelie-batteries. Nothing about the boss itself has changed, however.
In KSSU's Meta Knightmare Ultra mode, the core can also be damaged by Meta Knight's Mach Tornado.
Kirby's Epic Yarn/Kirby's Extra Epic Yarn
At the end of the Battleship Halberd stage Kirby uses his Starship transformation to traverse a long hallway. At the end the reactor core appears. It consists of two yellow main compartments: one at the top and one at the bottom of the hallway, each with three spikes with yellow balls on top, with a large green-colored gem in between them. Both compartments have one large cannon on it which shoots fire. Every once in a while, a UFO enemy will appear to impede Kirby's progress. The background shows grates, gears and panels. The goal is to destroy the two cannons, and then the gem. After this, the stage soon ends.
- Fire: The main attack comes from the two cannons, each spouting a straight line of fire reaching all the way across the screen.
- UFO: Every once in a while, a UFO enemy will appear from the top of the screen. It rapidly shoots three lasers, but can be destroyed.
- In all games it appears in, the reactor is the final hurdle before engaging Meta Knight.
- The Kirby Super Star (Ultra) version of the Reactor is the only boss (to date) that can in no way be harmed by Kirby, but only by its own attacks.
- In both versions of Revenge of Meta Knight, Sailor Waddle Dee specifies that a 'reflected' laser will damage the reactor core. However, in truth, the laser does not need to be reflected to do damage.